Improve tools/make_test_data.sh correctness

This change allows the script tools/make_test_data.sh and
tools/make_test_data.py to work correctly by handing
exceptions appropriately.


Change-Id: Ib054c3e10d617686928bf03f94c5ff868905afde
Closes-bug: 1389684
Merge "Improve tools/make_test_data.sh correctness"